1. Field of the Invention
The present invention relates to the design of a solar water heating system. More particularly, the present invention relates to a design of a complete solar water heating system including the solar energy collector and associated automatic control system in response to the rapid changing sunny-cloudy-raining weather changes to achieve the efficient usage of solar energy, and provide low cost and reliable heated water for daily use
2. The Prior Art
Solar power is a huge blessing from the mother nature to humankind. On average, solar energy falls on earth is about 2 calories per square centimeter per minute. This is equivalent to burning 100 million tons of good coal per minute. The effective use of this energy would help preserve the fossil fuel resources. It would lead to saving of fuel cost otherwise would be required for heating water or generating electric power. It would also reduce emission of polluting gas such as CO2, reducing the greenhouse effect on earth.
The coal being used today came from the trees existed several hundred million years ago using the solar energy available then to help tree grow. So, using the coal today is actually using the solar energy stored in the trees existed 100 millions years ago.
Traditionally the fossil fuel such as natural gas, coal, wood, and electricity are used for heating water to produce hot water. But the reserves of fossil fuel are limited. The more fossil fuel are burned, the more fuel reserve will go down and more pollution gas CO2 will be generated. With an estimation of only 100 more years of world oil supply, 80 more years of available nuclear fuel, 100 years of natural gas reserve and 300 more years of coal supply are left, the potential of the solar energy available should be actively pursued and utilized. One way to help achieve this object is to build solar water heating system for general household. It would reduce the consumption of available fossil fuels and the electricity used for heating water. The saved fuel and the electricity could be used for other good purposes. The mining activities for fossil fuel could be reduced. It would save cost of mining and preserve natural resources. It would also reduce emission of additional CO2, and mitigate the life and environment threatening problem of global warming. The solar energy is abundant and free, it should be actively utilized.
The development of solar energy usage technology has been in progress for many years. Many solar power projects have been planned and/or built with large amount of investment. However, the results have been less than satisfactory. The photovoltaic technology using silicon plate has been proven to be expensive. The manufacturing process for silicon plate is delicate and therefore expensive. Then, under strong bombardment of ultra-violet (UV) radiation, the high cost silicon solar panels deteriorate before the investment capital could be recovered. Its effective system life is often not as predicted. The returns on invested capital are mostly lower than the original investment. It is not cost effective. Many solar power plants have been abandoned during construction, or after short term operation. Generally, the bankers are hesitant to commit capital to solar power plant project because the capital returns are less than anticipated. Presently many solar silicon panel manufacturers worldwide failed financially. This is a disadvantage for solar energy industry. The vast amount of solar energy has not been continuously utilized day after day. This invention is devised to offer a way to harness the solar energy effectively, practically and at low cost.
The emphasized objects in the proposed equipment and system are: effective use of solar energy, low cost, reliable, low maintenance, long life, and easy to use.
The proposed solar energy collector is using the same idea as given in the patent application by the same author, title as “A Design of Dual Sources Solar Thermal Power Plant”. That is made from the aluminum body covered by a sheet of glass, and encased by effective insulation material. The glass is to pass the sun light and prevent massive heat loss back to atmosphere. A flat bottom of aluminum is painted black or by anodized aluminum coating. The water flow is through a hole near bottom of the aluminum body while absorbing heat from the body.
The weather conditions in each geological area are generally different. In some areas, there are always sunshine, while other areas would have weather condition changing from sunshine, to cloudy, and to raining. So the proposed equipment and system should be applicable to suit all different weather conditions. The solar energy collection is only possible during sunshine. Therefore a quick response automatic control system is required to control the system to follow the weather changes and adjust the system to best suit the latest conditions, producing the best results. Another important purpose of the automatic control feature is to minimize the human-machine interfaces. This would save many human hand-on control, minimize chance of human action errors. The automatic control system will includes a centralized control panel, a timer, a photo sensor to check if it is sunshine, small water pumps, three water temperature sensors, three water level switches, water flow sensor, air valve, auxiliary relays and water flow control valves. These control equipment and sensors will respond to changing weather conditions, and automatically perform the water heating process, or stop the system solar collecting process when it is raining or a cloudy day.
An insulated hot water tank is provided to store the solar heated water for household use. The tank will be provided with two high water level switches and a low water level switch. Two high level switches would be set at high-high positions. When the hot water level is at high-high, the high level signal will be sent out, stop the system process since the hot water tank is full, no more hot water is needed. The low water level switch will be used to stop the pump-out operation when water tank is almost empty.
The households still need hot water for bath or other use during raining or cloudy day where solar power is not available, therefore a standby gas (or propane) water heater should be provided. A selecter switch will be provided to select operation mode between solar power and gas power. An off position is also provided to shutdown the whole system, for cases like the vacation time and whole family is absent.
The equipment in the system are solid, simple and reliable, the system is expected to be practical.
No fancy equipment is required. The system cost is low and affordable. It has a capability of long term operation. It is necessary that the system cost must be reasonable low and the system is durable for long term operation. The economy of the system and the long term effective operation are crucial to make the system practical.